This invention relates to dipping processes for making various articles by dipping a form or pattern in a bath or slurry whereby the liquid coats the pattern and subsequently forms a thin membrane of the desired shape. More particularly, the invention relates to an apparatus for transporting and dipping the forming patterns in a continuous process through an operating cycle that includes lowering the pattern into the liquid bath to form a coating on the pattern, curing the coating to form a thin membrane, and then removing the resulting product from the pattern. The cycle is generally repeated on a continuous basis.
The manufacture of rubber gloves and other products formed of a thin, flexible membrane is often accomplished by dipping a form or pattern in an uncured liquid latex, usually at an elevated temperature, to coat the pattern with the latex. Then the coated pattern is removed from the bath and the latex cured thereon. The resulting product, in the form of a thin, flexible membrane of the desired shape, is then removed from the pattern.
Rubber gloves for physicians and dentists are typical products made by this method.
The equipment used for the process described generally includes an elongated tank containing a slurry of the latex material. A succession of patterns, such as handshaped forms suspended downwardly from a carrier bar, are conveyed horizontally along a linear span parallel to the tank and lowered into the bath. Then, the patterns are moved longitudinally a certain distance while immersed in the bath and raised out of the tank with a coating of the latex thereon.
The coated patterns are then conveyed past the tank through a curing zone, after which the thin, flexible membrane is removed and the pattern recycled back to the tank. This process is preferably performed on a continuous basis.
In many systems, the patterns are inverted after removal from the tank so that the product is cured with the pattern in an upright position relative to the pattern support member.
A typical conveying apparatus for the patterns utilizes an endless roller chain assembly with a horizontal path of travel, and with the roller chains extending between vertical axis drive sprockets at one end and vertical axis idler sprockets at the other.
The chain rollers have vertical axes which are unsupported in their respective spans between sprockets. A series of pattern carriers are connected to the roller chain assembly at spacings usually equal to the pitch of the chain. The pattern carriers include the pattern supports which extend perpendicular to the path of travel and which support the patterns with their greatest horizontal width dimension extending parallel to the path of travel.
The carriers have means, such as cam rollers and cam rails, for raising and lowering the pattern supports in response to the horizontal travel of the roller chain. In the prior art practice, the patterns (e.g., hand-shaped forms) have been arranged in a single row on the support, with the patterns' maximum width dimension aligned with the direction of travel. One support and its carrier have been connected to each chain link. With this arrangement, the width of the pattern is necessarily less than the pitch of the chain. Otherwise, the patterns would interfere with one another.
In actual practice, the width of the patterns must actually be significantly less than the pitch of the roller chain, or at least significantly less than the spacing between adjacent pattern carriers on the roller chain. This is necessary because the limited amount of free play of the pattern carriers could result in contact between patterns on adjacent pattern supports. This is likely to occur during the mechanical process of raising the patterns out of the dip tank. If contact occurs, the cured products on both of the contacting patterns must be scrapped.
Such incidents of pattern contact are especially likely to occur in high-speed operations. Some systems operate with conveyor speeds of as high as 45 feet per minute, and the complexity of movement affords many opportunities for contact between patterns in view of the inertial forces that occur.
The improved pattern carrier construction of the present invention, however, reduces the difficulties indicated above and affords other features and advantages heretofore not obtainable.